Cytoskeletal architecture differentially controls post-transcriptional processing of IL-6 and IL-8 mRNA in airway epithelial-like cells

Knockdown of Transmembrane Protein 150A (TMEM150A) Results in Increased Production of Multiple Cytokines

Lipopolysaccharide (LPS)-induced signaling through Toll-like receptor 4 (TLR4) is mediated by the plasma membrane lipid, phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P₂] and its derivatives diacylglycerol and inositol trisphosphate. Levels of PI(4,5)P₂ are controlled enzymatically and fluctuate in LPS-stimulated cells. Recently, transmembrane protein 150A (TMEM150A/TM6P1/damage-regulated autophagy modulator 5) has been shown to regulate PI(4,5)P₂ production at the plasma membrane by modifying the composition of the phosphatidylinositol 4-kinase enzyme complex. To determine if TMEM150A function impacts TLR4 signaling, TMEM150A was knocked down in TLR4-expressing epithelial cells and cytokine expression quantified after LPS stimulation. In general, decreased expression of TMEM150A led to increased levels of LPS-induced cytokine secretion and transcript levels. Unexpectedly, knockdown of TMEM150A in a lung epithelial cell line (H292) also led to increased cytokine levels in the unstimulated conditions suggesting TMEM150A plays an important role in cellular homeostasis. Future studies will investigate if TMEM150A plays a similar role for other TLR agonists and in other cell lineages.

Secreted MbovP0145 Promotes IL-8 Expression through Its Interactive β-Actin and MAPK Activation and Contributes to Neutrophil Migration

Mycoplasma bovis (M. bovis) is an important pathogen of cattle responsible for huge economic losses in the dairy and beef industries worldwide. The proteins secreted by M. bovis are mainly related to its adhesion, invasion, virulence, and intracellular survival and play a role in mycoplasma-host interactions. In our previous study, we found MbovP0145, a secreted protein present in the M. bovis secretome, but little is known about its function. In this study, we assessed the inflammatory characteristics and underlined mechanism of this inflammation of recombinant MbovP0145 (rMbovP0145). For this, bovine lung epithelial cells (EBL) were stimulated by rMbovP0145 to see the IL-8 production in a time- and dose-dependent manner. We observed that rMbovP0145 increased the production of IL-8 via ERK1/2 and P38 pathway activation. Further, the effect of the M. bovis ΔMbov_0145 mutant and its complementary strain on IL-8 mRNA expression was also confirmed. A pulldown assay of the GST-tagged MbovP0145 protein with mass spectrometry demonstrated that β-actin could specifically interact with rMbovP0145 to mediate the IL-8 signaling. As knockdown of β-actin expression with RNA interference in EBL cells decreased the mRNA expression of IL-8 and the phosphorylated ERK1/2 and P38 proteins, whereas disrupted actin polymerization by cytochalasin D led to a significantly higher IL-8 expression and MAPK phosphorylation in rMbovP0145-stimulated cells. Compared to M. bovis HB0801 and its complementary strain, the culture supernatant of EBL cells infected with the M. bovis ΔMbov_0145 mutant induced less neutrophil migration to the lower chamber in a transwell system. In conclusion, MbovP0145 promoted IL-8 expression by interacting with β-actin through activation of the MAPK pathway, thus contributing to neutrophil migration.

Paclitaxel-eluting silicone airway stent for preventing granulation tissue growth and lung cancer relapse in central airway pathologies

BACKGROUND

Airway stents are used to treat obstructive central airway pathologies including palliation of lung cancer, but face challenges with granulation tissue growth. Paclitaxel is a chemotherapy drug that also suppresses growth of granulation tissue. Yet, side effects arise from administration with toxic solubilizers. By incorporating paclitaxel in silicone stents, delivery of paclitaxel can be localized, and side effects minimized.

METHODS

Paclitaxel was incorporated into Liquid Silicone Rubber (LSR) containing polydimethylsiloxane, either as a powder or solution, prior to curing. Drug release study was compared in vitro at 37°C over 10 days. Drug release was quantified using HPLC, and bronchial cell lines were grown on LSR to investigate drug cytotoxicity, and expression of inflammatory markers, specifically interleukin-6 and interleukin-8.

RESULTS

Release rate of paclitaxel incorporated into silicone rubber was consistent with the Korsmeyer and Weibull models (R² > 0.96). Paclitaxel exposure reduced IL-8 levels in cancer cell lines, whilst no cytotoxic effect was observed in all cell lines at treatment concentration levels (≤ 0.1% (w/v) paclitaxel in silicone).

CONCLUSIONS

Incorporating paclitaxel into a silicone matrix for future use in a tracheobronchial stent was investigated. Drug release from silicone was observed and is a promising avenue for future treatments of central airway pathologies.

Novel aspects of T3 actions on GH and TSH synthesis and secretion: physiological implications

Thyroid hormones (THs) classically regulate the gene expression by transcriptional mechanisms. In pituitary, the encoding genes for growth hormone (GH) and thyroid-stimulating hormone (TSH) are examples of genes regulated by triiodothyronine (T₃) in a positive and negative way, respectively. Recent studies have shown a rapid adjustment of GH and TSH synthesis/secretion induced by T₃ posttranscriptional actions. In somatotrophs, T₃ promotes an increase in Gh mRNA content, poly(A) tail length and binding to the ribosome, associated with a rearrangement of actin cytoskeleton. In thyrotrophs, T₃ reduces Tshb mRNA content, poly(A) tail length and its association with the ribosome. In parallel, it promotes a redistribution of TSH secretory granules to more distal regions of the cell periphery, indicating a rapid effect of T₃ inhibition of TSH secretion. T₃ was shown to affect the content of tubulin and the polymerization of actin and tubulin cytoskeletons in the whole anterior pituitary gland, and to increase intracellular alpha (CGA) content. This review summarizes genomic and non-genomic/posttranscriptional actions of TH on the regulation of several steps of GH and TSH synthesis and secretion. These distinct mechanisms induced by T₃ can occur simultaneously, even though non-genomic effects are promptly elicited and precede the genomic actions, coexisting in a functional network within the cells.

Actin dynamics shape microglia effector functions

Impaired actin filament dynamics have been associated with cellular senescence. Microglia, the resident immune cells of the brain, are emerging as a central pathophysiological player in neurodegeneration. Microglia activation, which ranges on a continuum between classical and alternative, may be of critical importance to brain disease. Using genetic and pharmacological manipulations, we studied the effects of alterations in actin dynamics on microglia effector functions. Disruption of actin dynamics did not affect transcription of genes involved in the LPS-triggered classical inflammatory response. By contrast, in consequence of impaired nuclear translocation of phospho-STAT6, genes involved in IL-4 induced alternative activation were strongly downregulated. Functionally, impaired actin dynamics resulted in reduced NO secretion and reduced release of TNFalpha and IL-6 from LPS-stimulated microglia and of IGF-1 from IL-4 stimulated microglia. However, pathological stabilization of the actin cytoskeleton increased LPS-induced release of IL-1beta and IL-18, which belong to an unconventional secretory pathway. Reduced NO release was associated with decreased cytoplasmic iNOS protein expression and decreased intracellular arginine uptake. Furthermore, disruption of actin dynamics resulted in reduced microglia migration, proliferation and phagocytosis. Finally, baseline and ATP-induced [Ca(2+)]int levels were significantly increased in microglia lacking gelsolin, a key actin-severing protein. Together, the dynamic state of the actin cytoskeleton profoundly and distinctly affects microglia behaviours. Disruption of actin dynamics attenuates M2 polarization by inhibiting transcription of alternative activation genes. In classical activation, the role of actin remodelling is complex, does not relate to gene transcription and shows a major divergence between cytokines following conventional and unconventional secretion.

Anti-inflammatory effects of dietary phenolic compounds in an in vitro model of inflamed human intestinal epithelium

Phenolic compounds (PCs) are considered to possess anti-inflammatory properties and therefore were proposed as an alternative natural approach to prevent or treat chronic inflammatory diseases. However their effects are not fully understood, particularly at the intestinal level. To further understand their mode of action at the molecular level during intestinal inflammation, an in vitro model of inflamed human intestinal epithelium was established. Different representative dietary PCs, i.e. resveratrol, ellagic and ferulic acids, curcumin, quercetin, chrysin, (-)-epigallocatechin-3-gallate (EGCG) and genistein, were selected. To mimic intestinal inflammation, differentiated Caco-2 cells cultivated in bicameral inserts, in a serum-free medium, were treated with a cocktail of pro-inflammatory substances: interleukin (IL)-1β, tumor necrosis factor-α, interferon-γ and lipopolysaccharides. The inflammatory state was characterized by a leaky epithelial barrier (attenuation of the transepithelial electrical resistance) and by an over-expression at the mRNA and protein levels for pro-inflammatory markers, i.e. IL-6, IL-8 and monocyte chemoattractant protein-1 (MCP-1), quantified by ELISA and by gene expression analysis using a low-density array allowing the evaluation of expression level for 46 genes relevant of the intestinal inflammation and functional metabolism. Treatment with PCs, used at a realistic intestinal concentration, did not affect cell permeability. In inflamed cells, the incubation with genistein reduced the IL-6 and MCP-1 overproduction, to ca. 50% of the control, whereas EGCG provoked a decrease in the IL-6 and IL-8 over-secretion, by 50 and 60%, respectively. This occurred for both flavonoids without any concomitant inhibition of the corresponding mRNA expression. All the PCs generated a specific gene expression profile, with genistein the most efficient in the downregulation of the expression, or over-expression, of inflammatory genes notably those linked to the arachidonic metabolism pathway. In conclusion, this study provides evidence that genistein and EGCG downregulate the inflammatory response in inflamed intestinal epithelial cells by a pathway implicating largely a post-transcriptional regulatory mechanism.